1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and an image recording apparatus.
2. Description of the Related Art
There have heretofore been available image recording apparatuses configured to eject ink onto a recording medium while causing a recording head having an ejection opening array in which a plurality of ejection openings for ejecting ink of the same color are arranged in a predetermined direction to scan in a cross direction crossing the predetermined direction to complete the formation of an image on the recording medium. Such image recording apparatuses adopt a method that uses multiple scans or passes across a unit area on a recording medium, called multi-pass recording method, to suppress or reduce degradation of image quality.
It is well known that the ejection of ink using the multi-pass recording method described above may cause a certain ejection opening to have a failure to eject ink, such as being unable to eject ink or ejecting ink in a reduced amount. If such an inoperative ejection opening that has a failure to eject ink is assigned recording data for ejecting ink, no ink will be ejected onto an area onto which ink normally would be ejected, resulting in the quality of the image being reduced. Japanese Patent Laid-Open No. 5-330082 describes the following technique to address the issue of the degradation of image quality described above. If a certain ejection opening which will eject ink during a certain scan has a failure to eject ink, the recording data for such an inoperative ejection opening that has a failure to eject ink is complementarily assigned to any other ejection opening capable of ejecting ink onto the same area as that of the inoperative ejection opening during a different scan to perform complementary recording.
It is also well known that a recent image recording apparatus of the type described above includes a recording head in which a plurality of ejection opening arrays for ink of the same color are arranged side-by-side in the cross direction described above, and performs control to eject ink onto a recording medium while conveying the recording medium with respect to the recording head in the cross direction. Such an image recording apparatus provides recording by using a single scan without adopting the multi-pass recording method while achieving the effect of suppressing or reducing degradation of image quality similar to that of the multi-pass recording method (hereinafter also referred to as the “multi-pass effect”).
The use of the recording head described above may result in the amount of conveyance of a recording medium periodically varying. Accordingly, the positions where ink drops ejected from different ejection opening arrays land in the cross direction may be periodically displaced, causing a reduction in image quality. The displacement of the landing positions of ink drops increases with the difference between the times at which ink drops land, or increases with the distance between the ejection opening arrays in the cross direction. To address this issue, Japanese Patent Laid-Open No. 2008-168629 discloses the following technique. Binary data indicating positions in which ink drops are ejected is distributed to each ejection opening array, and recording data used for the ejection of ink drops from each ejection opening array is generated by setting the proportion of a predetermined number of ejection opening arrays arranged in close proximity to each other (for example, two adjacent ejection opening arrays) to which the binary data is distributed among a plurality of (for example, four) ejection opening arrays to be higher than the proportion of the other ejection opening arrays to which the binary data is distributed.
If a recording operation is performed using certain ejection opening arrays located in close proximity to each other among a plurality of ejection opening arrays arranged on a recording head in order to suppress or reduce the periodic displacement of the landing positions of ink drops described above, a certain ejection opening arranged in the certain ejection opening arrays may also experience such a failure to eject ink as described above.
The degradation of image quality due to the failure in the ejection of ink may be reduced to some extent by the performance of complementary recording using an ejection opening in any other non-defective ejection opening array located at a position such that ink drops can be ejected onto the same area as that of the inoperative ejection opening which has experienced the failure in ejection of ink in the certain ejection opening arrays. However, depending on the substitute to which the recording data for the inoperative ejection opening is complementarily assigned, complementary recording may be performed using an ejection opening other than ejection openings located in close proximity to the inoperative ejection opening as described above. This may result in failure to suppress or even reduce the displacement of the landing positions of ink drops.